A limnological study of the Sesan River - NIVA

STRIVER TECHNICAL BRIEF
Strategy and methodology for improved IWRM
- An integrated interdisciplinary assessment in four twinning river basins
TB No. 12
A limnological study of the Sesan River in
Cambodia in the dry season: focus on toxic
cyanobacteria and coliform bacteria
Chemical water analyses during the dry period in year
2008 (NE Cambodia) show that the trophic level in
Sesan was oligotrophic. Surprisingly, we found that a
large portion of the phytoplankton volume in the river
consisted of indicator species for a mesotrophic to
eutrophic environment; indicating influence from
upstream sources. More specifically, cyanobacteria and
especially toxic species was detected in addition to high
levels of thermo- tolerant coliform bacteria.
The STRIVER Brief series translate the results from the EC FP6-funded STRIVER project into
practical and useful information for policy makers and water managers

A limnological study of the Sesan River in Cambodia in
the dry season: focus on toxic cyanobacteria and
coliform bacteria
Anna Madeleine Tiodolf, Norwegian University of Life Sciences
Per Stålnacke, Bioforsk, Norway
Abstract
The Sesan River is one of the largest tributaries of the Mekong River. The river is a major
drinking water supply for the local people along river in the Ratanakiri province (North
East Cambodia). In 1996, Vietnam started an expansion of hydropower plants in the
Sesan River system. This has resulted in large changes downstream with uneven water
flow, increased erosion, decreased fish supply and polluted water. Through interviews
with inhabitants along the river we learnt that they periodically have health problems
after contact with the water in the river. The symptoms are mainly gastric disorders and
skin eruptions, but respiratory problems have also been reported. The aim of this study
was to analyze the water quality in the Sesan River during the dry season, focusing on the
presence of cyanobacteria, algae toxins and thermo-tolerant coliform bacteria (especially
the indicator organism E.coli). In our study existence of cyanobacteria in the Se San River
during the dry season was confirmed. In addition, the algae toxin microcystin was
detected in the Sesan River water. In addition, the concentration of the thermo-tolerant
coliform bacteria was high; the indicator organism E.coli being 10 3 -10 6 CFU ml -1 which
indicate risk of water borne disease spreading.
References
This STRIVER Technical Brief is based on the following research reports and scientific literature:
Tiodolf A. M. 2009 A limnological study in the Se San River in Cambodia during the dry season: focus
on toxic cyanobacteria and coliform bacteria, Master thesis, Norwegian University of Life Sciences
(In Swedish with abstract in English and Khmer).
Method
Our field visit was conducted during a two-week period in March 2008. Water samples were taken
every second day in two different areas along the Sesan River; Adong Meas, 30 kilometers
downstream the Vietnamese border, and Veun Sai, about 130 kilometers downstream the Vietnamese
border (Fig.1). Water samples were also taken in three Cambodian tributaries. Each study area was
visited three times. Water for sampling was taken with a water-sampler or directly in a plastic
container from the surface water. In addition algae-samples were taken with a 25µm net haul.
Quantitative algae-samples and net haul samples were preserved by Lugol´s solution (fytofix) for
species composition. For analyzing algae toxin, 48 mm GF/C Wathman-filters were filtered with a
known amount of water and dried in darkness. To detect E.coli selective medium, MLGA and VRBA,
were used. The water-samples were filtered through 0,45 µm cellulose membrane filters and
cultivated on the selected medium in up to five days in an incubator-oven at 44ºC, distributed by
Colifast.
Meach Mean at 3SPN is acknowledged for all practical help during our field study
STRIVER TECHNICAL BRIEF / ISSUE NO. 12 2

Figure 1. Map over the study area. 1.The tributary O Kup, 2. Adong Meas, 3. Kachon, 4. The tributary
Vireak Chey National Park, 5. Veun Sai, 6. The tributary O Tang, 7-9 minor streams and one lake in
the Ban Lung area.
Figure 2. Water sampling at Adong Meas (upper left photo: G Bun) and Kachon (upper right photo: M.
Tiodolf); meeting with local people in Veun Sai 13th of March 2008 (lower left photo: M. Tiodolf); the
tributary river O Kup (lower right photo: M. Tiodolf)
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Figure 2. The catchment area of the Sesan River
(Berge&Nhung, 2008).
The study area
The Sesan River is one of the largest
tributaries of the Mekong River (Fig. 3) and
has a drainage area of 17,000 square km,
where of 11,000 square km in Vietnam and
6,000 square km in Cambodia. Most population
living in the basin are made up of ethnic
minority groups that rely heavily on the river
for subsistence agriculture, fishing, and
developing techniques suited for small-scale
water utilization.
Cyanobacteria in the Sesan River
Existence of cyanobacteria in the Sesan River
during the dry season was in our study
confirmed (Fig. 4). More specifically, colonies
of Microcystis sp. species (Fig. 5) was
established in quantitative analysis of water
samples. Colonies of Microcystis sp. but also
cellular fibres of Planktothrix sp. and
Aphanizomenon sp. was confirmed in the
qualitative analysis of net haul samples.
Colonies of Pseudoanabena sp. have been
established in cultures of water samples with
Blue-Green agar.
Figure 4. Average density of Cyanobacteria in
the qualitative analysis of net haul samples
from Adong Meas (upper panel), Kachon
(middle panel) and Veun Sai (lower panel). NB!
A maximum value of 32 means a total
dominance of a particular algae in the sample.
STRIVER TECHNICAL BRIEF / ISSUE NO. 12 4

ivers showed dominance of Chrysophyceae
and µ-algae (Fig. 9).
Also noteworthy was that cyanobacteria made
up a maximum of 3% of the algae composition
in the quantitative samples from the main
stream (Fig. 8; water samples from Adong
Meas) while no cyanobacteria was detected in
the local tributaries.
Figure 5. A colony with Microcystis sp. from the
water samples taken in the Sesan River
suggested to be Microcystis botrys by
Associate Professor Gertrud Cronberg, Lund
University. Photo: R. Ptacnik (NIVA)
Cyanotoxins in the Sesan River
Concentrations of the algae toxin microcystin
(hepatoxin) (Table 1) exceeded the WHO limit
for drinking water (1 µg L -1 ) and approach the
limit for safe bathing (10 µg L -1 ).
The most commonly registered symptoms
shown by people exposed to cyanotoxins are
allergic reactions i.e. fever, skin irritation and
diarrhoea. Microcystin is toxic to the liver and
can cause injury or cancer in the liver after a
longer period of exposure.
Through interviews with the inhabitants along
the Sesan River we learn that irritation of the
skin (Fig. 6) and gastric disorders are
commonly occurring after bathing in the river,
especially during the dry season.
Figure 6. A child with skin-problem living in
Adong Meas (2) claimed to be caused by
contact with the Sesan River water. Photo: M.
Tiodolf
Algae composition
Both the algae and chlorophyll concentrations
were different between the main stream and
the local tributaries (Fig. 7).
Moreover, the algae composition in the
analyzed water samples and net haul samples
from the main Sesan River show predominance
of the algae groups Dinophyceae,
Chrysophyceae and Bacillariophyceae (Fig. 8).
Many of the specific species within these
groups indicate a euthrophic environment. On
contrary, the samples from the local tributary
Figure 7. Difference in the algae and
chlorophyll a concentrations in water samples
from the Sesan River (main stream) compared
to water samples from the three tributaries
(March 2008).
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Figure 8. Algae composition in quantitative
analyses of water samples from the Sesan River
(main river) sampled in Adong Meas (upper
panel), Kachon (middle panel) and Veun Sai
(lower panel).
Figure 9. Algae composition in quantitative
analyses of water samples from the tributaries
O Kup (upper panel), Vireak Chey National Park
(middle panel) and O Tang (lower panel).
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Thermo-tolerant coliform bacteria
The concentration of thermo-tolerant coliform
bacteria was high; the indicator organism
E.coli being 10 3 -10 6 CFU ml -1 (Table 2).
This indicates risk of spreading of waterborne
diseases. WHO´s limit for E.coli or thermo
tolerant coliform bacteria is that they should
not occur in a 100 ml water sample.
Similar levels of bacteria concentration has
been found through analysis of water samples
in other tropical areas, for example Uganda,
South Africa and India. Analyses of river water
in Lebanon have shown concentrations up to
6 x 10 4 CFU ml -1 alongside with a significant
health effect on people bathing in the river.
Bathers got skin reactions, which is one of the
main health problems that the locals along the
Sesan River experience in connection with
bathing.
“When waters are released,
sediment of construction materials,
such as rock, soil, concrete and dead
animals, such as small fish, snakes,
turtles and frogs passed through
turbines are factors with long-lasting
effects on local people´s life
downstream .... That‟s why the
water is called „cement water‟ ”
CHRES. 2001. Study into impacts of Yali Falls
Dam on resettled and downstream
communitie. Vietnam National University
Water chemistry
Chemical water analyses show that the Sesan
Rivers nutrient level is oligotrophic during the
dry period (Table 3). However, the water
samples from the tributaries O Kup and O
Tang show higher phosphorous concentrations
and in some cases indicate a eutrophic trophic
level.
Figure 10. Sampling of foam floating on the
Sesan River (March 2008). Photo: P. Stålnacke
Conclusions
The following conclusions can be drawn from
the sampling in March 2008:
Occurrence of cyanobacteria and
cyanotoxins in the main stream of the
Sesan River was confirmed.
No cyanobacteria in the water samples
taken in three different tributaries were
detected.
The algae composition in the main stream
of the Sesan River indicate a mesotrophic
to eutrophic environment. The reason for
this could be that the algae originate from
more stagnant water, with higher nutrient
concentrations, i.e., originating further
upstream in the Sesan River.
In contrast to the algae composition
results, the water chemistry analyses in the
main stream of Sesan River show an
oligotrophic trophic level.
According to the WHO limits, the results of
this study show the drinking quality of the
water in the Sesan River is not suitable for
human consumption. More specifically, the
content of thermo-tolerant coliform bacteria
and the indicator organism E.coli along with
the levels of cyanotoxin microcystins were
found to be too high.
STRIVER TECHNICAL BRIEF / ISSUE NO. 12 7

Supplementary data tables
Table 1. Concentrations of the cyanotoxin microcystin in water samples analyzed by an anti-adda
ELISA kit (ABRAXIS, product no. 520011) at the NIVA-laboratory (Norway).
Tributary
Locality Date Filtrated amount Concentration of
March
of water
Microcystin
2008 (L) (µg L -1 )
O Kup (1) 14 1,27 *
O Kup (1) 14 1,05 *
O Kup (1) 16 1,00 *
O Kup (1) 16 1,08 *
O Kup (1) 18 1,00 *
O Kup (1) 18 1,00 *
Se San
Adong Meas (2) 14 1,20 5,23
Adong Meas (2) 14 1,30 8,39
Adong Meas (2) 16 1,62 *
Adong Meas (2) 16 1,88 6,96
Adong Meas (2) 18 1,00 *
Adong Meas (2) 18 1,00 *
Se San
Kachon (3) 13 1,00 *
Kachon (3) 13 1,00 *
Kachon (3) 15 1,17 *
Kachon (3) 15 1,52 5,58
Kachon (3) 17 1,00 *
Kachon (3) 17 1,00 *
tributary
Vireak Chey National Park
(4) 15 0,75 ( ?) *
Vireak Chey National Park
(4) 15 0,75 *
Vireak Chey National Park
(4) 17 0,75 *
Vireak Chey National Park
(4) 17 0,75 *
Se San
Veun Sai ( 5) 13 0,73 *
Veun Sai ( 5) 15 1,00 *
Veun Sai ( 5) 15 1,05 *
Veun Sai ( 5) 17 0,85 *
Veun Sai ( 5) 17 0,85 *
Tributary
O Tang (6) 13 1,00 *
*) Concentrations below LOD (limit of detection)
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Table 2. Water samples cultivated on the selective medium MLGA. Green colonies are E.coli and
yellow colonies are thermo-tolerant coliform bacteria, which are not E.coli.
Locality Date Cultivating Thermo-tolerant coliform bacteria
March days yellow colonies green colonies total
2008 42-44º C (CFU 100ml -1 ) (CFU 100ml -1 ) (CFU 100ml -1 )
Tributary
O Kup (1) 14 3 * 33 x 10 5 33 x 10 5
O Kup (1) 16 5 * 20 x 10 5 20 x 10 5
O Kup (1) 18 1 ##
Se San
Adong Meas (2) 14 3# * 10 x 10 6 10 x 10 6
Adong Meas (2) 16 5 * 17 x 10 5 17 x 10 5
Adong Meas (2) 18 2 40 x10 5 * 40 x10 5
Se San
Kachon (3) 13 2,5# 21 x 10 4 * 21 x 10 4
Kachon (3) 15 2 * 21 x 10 4 21 x 10 4
Kachon (3) 17 4 ##
Tributary
Vireak Chey National park (4) 15 2 * 70 x 10 4 70 x 10 4
Vireak Chey National park (4) 17 2 9 x 10 ^5 8x 10 5 17 x 10 5
Se San
Veun Sai (5) 13 2# 40 x 10 4 * 40 x 10 4
Veun Sai (5) 15 2 * 20 x 10 5 20 x 10 5
Veun Sai (5) 17 2 ##
Tributary
O Tang (6) 13 2,5# 85 x 10 4 * 85 x 10 4
Other watersystems in
the Ban Lung area
Stream water (8) 17 1 14 x 10 4 1 x 10 4 15 x 10 4
Kan San (9) 16 5 90 x 10 4 * 90 x 10 4
*) No growth of thermo-tolerant coliform bacteria.
#) Samples cultivated in 25-35ºC.
##) Not countable cultures due to too high concentrations of bacterial colonies.
STRIVER TECHNICAL BRIEF / ISSUE NO. 12 9

Table 3. Chemical analyses of water quality at various sites (March 2008). Laboratory analyses
performed at Norwegian University of Life Sciences.
Tributary
Locality Date Chl a TOC Tot-N Tot-P Turbidity Conductivity
March 2008 (mg L -1 ) (mg L -1 ) (µgN L -1 ) (µg P L -1 ) (NTU) (mS m -1 )
O Kup (1) 14 0,5 1,4 130 31,6 12,1 4,3
O Kup (1) 16 0,4 1,5 230 32 15,7 4,5
O Kup (1) 18 0,5 1,6 116 23,2 6,9 4,4
Se San
Adong Meas (2) 14 3,2 0,8 160 3,5 1,8 4,0
Adong Meas (2) 16 3 0,8 160 3,9 2,9 4,1
Adong Meas (2) 18 2,7 1,1 190 4,9 1,3 4,2
Se San
Kachon (3) 13 4 0,8 160 4,2 1,6 3,9
Kachon (3) 15 4,2 0,7 140 3,2 3,1 3,8
Kachon (3) 17 3,8 0,8 150 4,2 2,2 3,9
Tributary
Vireak Chey national park
(4) 15 1,1 0,8 110 3,5 1,9 2,5
Vireak Chey national park
(4) 17 1,4 0,9 110 3,5 2,4 2,5
Se San
Veun Sai (5) 13 4,1 0,8 170 4,6 2,8 3,9
Veun Sai (5) 15 4,2 0,7 130 3,9 3,0 4,0
Veun Sai (5) 17 3,9 0,7 150 4,2 1,7 4,0
Tributary
O Tang (6) 13 0,6 1,6 200 10,5 3,8 10,1
Table 4. Selected results from metal compounds at various sites (March 2008). Laboratory analyses
performed at Norwegian University of Life Sciences.
Locality Date Aluminium Copper Iron Lead Zink
Tributaries
Al Cu Fe Pb Zn
March OES MS OES MS MS
2008 (µg L -1 ) (µg L -1 ) (mg L -1 ) (µg L -1 ) (µg L -1 )
O Kup (1) 14 80 1,4 0,94 0,21 2,9
O Kup (1) 16 120 2,4 1,1 0,36 3,9
O Kup (1) 18 120 4,5 1,3 0,45 12
Vireak Chey National Park (4) 15 30 0,3 0,55 0,35 2,1
Vireak Chey National Park (4) 17 40 0,4 0,55 0,18 1,2
Se San
Veun Sai (5) 13 100 0,9 0,2 0,22 0,9
Veun Sai (5) 15 90 0,8 0,21 0,24 1,4
Veun Sai (5) 17 50 0,8 0,12 0,13 1,1
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The STRIVER Policy and Technical Brief series translate the
results from the project into practical and useful information for
policy makers and water managers.
The Briefs are also available online: www.striver.no
About STRIVER
STRIVER- Strategy and methodology for improved IWRM - An
integrated interdisciplinary assessment in four twinning river basins
is a three year EC funded project 2006-2009 under the 6th
framework programme (FP6) coordinated jointly by Bioforsk and
NIVA. The point of departure for STRIVER is the lack of clear
methodologies and problems in operationalisation of Integrated
Water Resource Management (IWRM) as pointed out by both the
scientific and management communities.13 partners from 9
countries participate as contractual partners in addition to an
external advisory board.
Title of project:
Strategy and methodology for improved IWRM
- An integrated interdisciplinary assessment in four twinning river
basins (STRIVER)
Instrument: SUSTDEV-2005-3.II.3.6: Twinning European/third
countries river basins.
Contract number: 037141
Start date of project: July 2006 Duration: 36 months
Project funded by the European Commission within the Sixth
Framework Programme (2002-2006)
Disclaimer
The information provided and the opinions given in this publication
are not necessarily those of the authors or the EC. The authors and
publisher assume no liability for any loss resulting from the use of
this report.
Front-cover photos: Rinsing a chicken along the Sesan River in
Cambodia (Left photo: M. Tiodolf), Micrasterias foliacea algae in the
Sesan River (Middle photo: R. Ptacnik), local woman washing
clothes along the Sesan River (Right photo: M. Tiodolf)
Launch-date: 17 August, 2009